Sheet feeder

ABSTRACT

A separation belt is supported for movement about entrance and exit pulleys with a section of the belt between the pulleys positioned against curved retard means forming a sheet queuing throat. The belt contacts a stack of sheets near its edge and separates the sheets from the stack into the throat. The throat queues or aligns the sheets and the belt advances the queued sheets onto the sheet handling system being served.

[111 3,768,803 1 Oct. 30, 1973 1 SHEET FEEDER [75] Inventor: Klaus K. Stange, Pittsford, NY.

[73] Assignee: Xerox Corporation, Stamford,

Conn.

[22] Filed: Feb. 11, 1972 [21] Appl. No.: 225,513

[52] US. Cl. 271/34 [51] Int. Cl B65h 3/04 [58] Field of Search 271/34, 35, 26 F, 271/6 [56] References Cited UNITED STATES PATENTS 3,485,489 12/1969 Lindquist 271/34 X 3,126,199 3/1964 Rosoff 271/35 X 3,219,339 11/1965 Gutierrez.. 271/34 X 861,367 7/1907 Jahn 271/6 3,069,157 12/1962 Mersereau et al... 271/34 X 3,520,532 7/1970 Towne 271/34 3,655,183 4/1972 Wagner..... 271/39 X 3,533,617 10/1970 Collins 271/61 X FOREIGN PATENTS OR APPLICATIONS 1,068,162 6/1954 France 271/35 668,004 l1/l938 Germany 271/34 OTHER PUBLICATIONS Albo, R. T. Single Sheet Paper Feed." IBM Technical Disclosure Bulletin. Vol. 8, No. 10, March 1966. P. 1431.

Coudill, A. H. and W. H. Jenkins. Sheet Paper Feed System. IBM Technical Disclosure Bulletin. Vol. 14, No.5, Oct. 1971. P. 1455.

Primary Examiner-Evon C. Blunk Assistant Examiner-Bruce l-I. Stoner, Jr. Attorney-James J. Ralabate et al.

[57] ABSTRACT A separation belt is supported for movement about entrance and exit pulleys with a section of the belt between the pulleys positioned against curved retard means forming a sheet queuing throat. The belt contacts a stack of sheets near its edge and separates the sheets from the stack into the throat. The throat queues or aligns the sheets and the belt advances the queued sheets onto the sheet handling system being served.

11 Claims, 24 Drawing Figures Patented Oct. 30, 1973 3,768,803

9 Sheets-Sheet 1 Patented Oct. 30, 1973 3,768,803

9 Sheets-Sheet 2 FIG. 34

FORCE 3/ FORCE FIG. 30

Patented Oct. 30, 1973 3,768,803

9 Sheets-Sheet 5 Patented Oct. 30, 1973 3,768,803

9 Sheets-Sheet 4 Patented Oct. 30, 1973 3,768,803

9 Sheets-Shoot i.

Patented Oct. 30, 1973 r9 Sheets-Sheet 6 'lllllllllllq Patented Oct. 30, 1973 3,768,803

9 Sheets-Sheet 7 Patented Oct. 30, 1973 3,768,803

9 Sheets-Shoe L :1

FIG. /4

89 llIII/III/m Patented Oct. 30, 1973 3,768,803

9 Sheets-Sheet 1) I I :mmmxmmmxm-x I I I I I I I I I I 4 FIG. [9

FIG. /8

SHEET FEEDER BACKGROUND OF THE INVENTION This invention relates to systems for handling sheets. More specifically, the instant invention relates to method and apparatus for feeding sheets from a stack.

Feeding sheets from a stack may be viewed as involving three separate problems. The first is separating a sheet or sheets from a stack. The second is queuing the separated sheets into an order such as that corresponding to their order in the stack, e.g. outermost sheets followed by the adjacent intermost sheets. The third problem is advancing the queued sheets into the sheet processing system being served by the feeding mechanism.

Accordingly, it is a primary object of this invention to devise method and apparatus for solving the foregoing sheet feeding problems.

More specifically, it is an object of this invention to enhance sheet handling by greatly simplying the method and apparatus for feeding sheets from a stack.

Another object of the invention consistent with the foregoing objects is to devise novel sheet handling method and apparatus that minimizes contact between the feeding mechanism and the sheets.

Still another object of the present invention is to feed sheets from a stack in a substantially fixed plane without substantially distorting the sheets during the feeding operation.

Even a further object is to devise economic sheet feeding method and apparatus of unique design.

Another object of this invention is to enhance the efficiency of sheet separating and queuing methods and apparatus.

Yet another object is to devise unique method and apparatus for separating sheets from a stack and for queuing the separated sheets.

Finally, it is also an object of this invention to devise novel sheet feeding method and apparatus utilizing a sheet separation belt and retard means.

The sheet separation belt and retard roller appear in the sheet handling art at least as early as 1916 in U. S. Pat. No. 1,167,367 to P. L. Wells and as recently as 1969 in U. S. Pat. 3,469,834 to Stange et al. The separation belt and retard roller are employed in these patents for queuing and advancing the sheets but not for separating them from the stack. In the patents, the region of contact between the roller and belt form a sheet queuing throat which is able to fan out or queue sheets passed through it. The sheets are separated from a stack and fed to the throat by a presser foot in the Wells, U.S. Pat. No. 1,167,367 and by a nudger or feed wheel in the Stange et al., U.S. Pat. No. 3,469,834.

In the present invention, the foregoing and other objects are realized by using a separation belt and retard means to perform all three functions of sheet separating, queuing and advancing. One unique feature of the instant invention is that the separation belt and retard means are positioned adjacent the edge of a stack of sheets. The belt contacts an outer sheet near the edge of the stack and pulls or separates this and possibly other sheets from the stack. The separated sheets travel a very short distance before reaching a sheet queuing throat because the retard means is positioned close to the edge of the stack. This basic technique minimizes the contact with a sheet yet is exceptionally effective in dealing with various sheet weights, materials, stack conditions and feeding environments.

DESCRIPTION OF THE DRAWINGS The foregoing and other features of the instant invention will be more apparent from a further reading of the specification and claims and from the drawings which are:

FIG. 1 is a side elevation view of one embodiment of the present invention.

FIG. 2 is a plan view partially in section of the apparatus in FIG. 1.

FIG. 3 is an enlarged side elevation view of the apparatus shown in FIG. 1.

FIG. 3A is an enlarged view of the separation belt and sheets shown in FIG. 3.

FIGS. 38 and 3C are diagrams illustrating coupling forces exerted on sheets in stacks of sheets of different beam strength.

FIG. 4 is an enlarged view of a sheet queuing throat formed according to the instant invention and a diagram of the normal forces associated with the throat.

FIGS. SA-C are enlarged views of the throat and adjacent regions illustrating the operation of the instant method and apparatus.

FIG. 6 is a view of an embodiment of the instant invention wherein the separation belt contacts a sheet in a stack beneath the outermost sheet.

FIG. 7 is a side elevation view of another embodiment of the instant invention employing a generally non-linear separation belt section to form a queuing throat.

FIG. 8 is a side elevation view of another embodiment of this invention illustrating means for imparting tension to a non-elastic sheet separation belt.

FIG. 9 is an isometric, exploded view of one embodiment of the retard means of the instant invention.

FIG. 10 is a front elevation view of the apparatus of the instant invention illustrating a preferred relationship between the separation belt and retard means.

FIG. 11 is a side elevation view of an embodiment of the instant invention including steering means for controlling the direction of a sheet.

FIG. 12 is a side elevation view of an another embodiment of the instant invention wherein the sheet separation belt has a finite length.

FIG. 13-15 are side elevation view of embodiments of the present invention illustrating various paper trays and feeding environments.

FIG. 16 is a side elevation view of yet another embodiment of the instant invention illustrating a unique mounting for the separation belt, the variation of the entrance angle to the queuing throat, a novel paper tray, advancing rollers and a retard means including a moving web.

FIG. 17 is a plan view of a separation belt having a tire tread pattern.

FIG. 18 is an end elevation view of the apparatus in FIG. 1.

FIG. 19 is a cross-section ofa fiber reinforced elastic separation belt.

DETAILED DESCRIPTION The unique method and apparatus of the present invention is illustrated in one embodiment by FIG. 1. The sheet feeding apparatus 1 includes the sheet separation belt 2 and the abutting retard means 3 which form a sheet queuing throat 4 in the region of contact between them. Sheets are separated from the stack 5 by contacting the stack with the belt and moving the belt over the stack toward the throat. The belt pulls or separates sheets from the stack and moves them through the throat which arranges them in single file corresponding to their order in the stack. The belt may also advance the queued sheets into the particular sheet processing system being served by apparatus 1.

The belt in the embodiment of FIG. 1 includes an endless loop of elastic material supported for movement about the entrance and exit pulleys 8 and 9. The novel retard means of FIG. 1 includes a stationary pad 10 of resilient material. Both surface 11 of the pad and the surface of the belt facing the pad have relatively high coefficient of frictions compared to the sheets. Surface 11 may include plane and/or curved surfaces which along with the belt form the queuing throat 4.

The relative position of the belt, stack and retard means are important features of the instant invention. The belt contacts the stack near the edge 12 so that the outermost sheet is almost entirely separated from the stack before the underlying sheet is contacted by the belt. This edge contact approach minimizes the stack depth to which intersheet coupling is increased by reason of the belt contact with the stack. Edge contact also means that the outermost sheet is acted upon by the belt for the longest practical time period before the underlying sheet is encountered. Consequently, the sepa? ration queuing and advancing operations are all very efficient.

Edge contact, as used herein, means belt contact with a stack not so far removed from an edge, e.g. edge 12, as to lose the foregoing and other benefits but also not so close to the edge to disrupt the integrity of the stack. The edge contact is preferably sufficiently removed from the edge so that sheets are not displaced from the stack in a direction opposite the feed direction under the force exerted on the stack by the belt and, for example, by the tray 13 supporting the stack. As a rule of thumb, the line 14 in FIG. 1 defines a region of contact which meets the foregoing criteria. Line 14 runs through the axis of the entrance pulley 8, is generally normal to the sheets in the stack and is very near the edge 12. This line roughly defines the direction of force exerted on the stack by mechanically biasing the entrance pulley 8 and tray 13 toward each other. Line 14 is sufficiently removed from edge 12 so as to intersect the majority of the sheets in the stack yet is approximately as close to edge 12 as is the entrance to throat 4.

As indicated above, the retard means (pad 10 in the case of FIG. 1) is located very close to the edge 12 and line 14 representing the point of contact between belt and stack. The length and width of apparatus 1 is preferably much smaller than the length and width of a sheet. The distance between the throat and edge 12 is preferably as close as possible, being limited in FIG. 1 by the dimensions of jaw and tongue members 17 and 18. The jaw and tongue members are formed from one metal piece in the embodiment of FIG. 1. The jaw is an abutment for limiting movement of the stack in the feed direction and the tongue is a support for guiding the separated sheets into throat 4 rather than downward parailel to edge 12.

Moving the belt over the stack and retard members causes the outer sheets to be pulled toward the throat. Since pad 10 is very close to edge 12, the separated sheets are immediately subjected to the queuing operation of the throat. The queuing process relies on the 1 fact that the coupling forces between the belt and outermost sheet are greater than the coupling forces between sheets. Underlying sheets pulled along into the throat are stopped by the retard pad until the outermost sheet is clear of the throat. Because of the close spacings in question relative to the dimensions of the sheets, the outermost sheet is almost clear of the throat when the belt contacts an underlying sheet near line 14. The underlying sheet is not buckled prior to the outermost sheet clearing the throat because, for one, only the lead edge of this sheet is subjected to any strain.

Before proceeding further, the terms sheet" and stack as used herein will be defined. Sheet specifically includes those sheet materials, e.g. paper, that are used in Xerographic machines. These sheets include very thin papers ranging from less than 9 to about 15 pounds of weight and from about 0.0017 to about 0.0025 inches of thickness. Xerographic sheets also include medium weight sheets of paper of from about l5 to about 32 pounds of weight and from about 0.0025 to about 0.0040 inches in thickness. Other Xerographic sheets include card or ledger stock of weights in excess of 32 pounds and thicknesses in excess of 0.0045 inches. Xerographic sheets also include various weight papers that are coated and/or impregnated with other materials such as plastics and/or photosensitive materials. Examples of the photosensitive materials include zinc oxide and cadmium sulfide. Since transparent plastic sheets are employed in Xerographic machines, they too are included with the present meaning of sheet. As a rule, the term sheet is intended to encompass those materials not mentioned which may or may not be in current use in Xerographic systems but which are adaptable to that use. The instant invention is not limited to xerography, however, so that the term sheet includes those sheet materials not mentioned which are susceptable to being separated from a stack, queued and advanced by the presently described method and apparatus.

Stack" means a pile of sheets either homogeneously or heterogeneously composed. In other words, a stack is a reservoir or supply of sheets each of the same or a different material arranged to more or less lie on top of one another. Normally, the stack or pile is reasonably well defined with a finite number or edges (e.g. an edge 12) equal to or greater than the number of sides to a sheet. Practically speaking, Xerographic machines would normally employ stacks comprising at least five sheets.

The operation of the present sheet feeding method and apparatus is depicted in FIG. 3 through FIG. 6. Some of the important parameters effecting sheet feeding include-(See FIG. 4): the normal force 20 exerted by the belt on the pad 10; the stack force 21 between the belt and stack; the wrap distance 22 which is the length of the queuing throat; the shape of the mouth 23 formed at the entrance to throat 4 by the belt and tongue 18; and the radius 24 of the pad surface 11. These parameters may be altered to accommodate different sheet materials. To feed the card stock type of sheets mentioned earlier, for example, the normal force 20 is relatively low, the stack force 21 is relatively high, and wrap distance 22 is very short (0.05-0.100 inches for example), the mouth 23 is comparatively large and the radius 24 is relatively long. To feed the medium sheet materials mentioned earlier such as the very familar 20 pound bond paper sheet, the parameters are adjusted relative to the card stock case to yield a larger normal force 20, a lower stack force 21, a larger wrap distance 22, a reduced mouth 23 but about the same radius 24. To feed the thin sheets mentioned earlier, the parameters are adjusted relative to the medium sheet case by slightly increasing normal force 20, slightly reducing stack force 21, substantially increasing the wrap distance 22 (i.e. increasing distance 22 by a factor of at least 1.5), reducing the size of mouth 23 but once again leaving the radius alone. To feed plastic sheets, sheets stuck together by strawberry jam, elec-.

trostatic forces, staples or other means such as rips and tears, the parameters are adjusted relative to the thin sheet case by increasing normal force 20, reducing stack force 21, increasing the wrap distance 22, changing the slope of tongue 18 to catch sheets with severely curled edges, thereby changing the shape of the mouth 23 and by shortening the radius 24.

Before the apparatus 1 is commanded to feed the first sheet, the normal force 20 is almost evenly distributed over the contact surface 11 of the retard means, i.e. pad in the case of FIG. 1. The stack force 21 (generated in one way by mechanically biasing entrance pulley 8 and tray 13 toward each other) is normally sufficiently adjusted to slightly deform some of the top sheets in the stack near the contact region around line 14 (See FIG. 3A). The belt 2 is also deformed under force 21 when it includes an elastic material thereby creating a strong coupling between the belt and sheet 31 (the outer sheets are labeled 31-35 respectively). In addition, stack force 21 creates an intersheet coupling. The intersheet coupling generated is influenced by the diameter of the entrance pulley 8, by the beam strength ofthe sheets and by the surface condition of the sheets. The sheet depth within the stack to which the intersheet coupling can be attributable to force 21 is minimized by keeping the surface areas of contact between belt and stack small. This includes limiting the contact region to near the edge of the stack (i.e. edge 12).

The curve 40 in FIG. 38 illustrates the intercoupling in a stack that results in a sequential feeding of sheets into the queuing throat. Curve 40 represents the situation of continuingly decreasing intercoupling force. Curve 41 in FIG. 3C illustrates the intercoupling forces that can result in several outersheets being simultaneously pulled into the queuing throat. A curve like curve 41 can be found where the sheets 31-35 have different beam strengths and/or surface conditions. The stack force 21 is usually selected to be sufficiently large so that the weight of the sheets does not contribute significantly to the intersheet coupling. Paper weight will normally not be a factor with apparatus 1 because the edge contact minimizes the number of sheets in the stack, i.e. stack depth, having the intersheet coupling force increased due to force 21.

To feed sheet 31 (FIG. 4), exit pulley 9 (which is preferably a drive pulley with pulley 8 being an idler) is accelerated. The belt section between pulley 9 and pad 10 is stretched followed by the stretching of the belt section in the throat 4 which in turn is followed by movement of the belt at the contact region around line 14. During the acceleration of pulley 9, normal force 21 is non-uniform in the throat 4 and may be somewhat as depicted by curve 42 in FIG. 4. Curve 42 will be discussed in more detail later.

FIGS. 5A, 5B and 5C illustrate the present separating and queuing operations for the worse case of intersheet coupling represented by curve 41 in FIG. 3C.

Sheets 31, 32 and 33 are advanced together by the belt to point 47 while sheets 34 and 35 are pulled along by sheets 31 and 32 to points 46 and 45 respectively (FIG. 5A). Consequently, points 47, 46 and 45 represent those places where the frictional forces between the pad 10 and sheets 33, 34 and 35 are equal or greater than the frictional forces coupling a sheet with the sheet above. The belt continues to advance sheets 31 and 32 to point 48 where the pad 10 succeeds in stopping sheet 32 (FIG. 5B). The outermost sheet 31 continues to be advanced by the belt until it clears the throat (FIG. 5C).

To fully appreciate some of the outstanding features of the instant method and apparatus it is helpful to conduct a simple experiment. Pinch several sheets of paper between a dry thumb and a moistened forefinger of the right hand. With light pressure, move the forefinger toward the palm of the hand and note the sheet separation. Now repeat the experiment but with a greatly exaggerated pinching force and compare the results to the first experiment. Pinching force, i.e. (force 20) and length of thumb (wrap distance 22) must be balanced to obtain optimum performance. A high initial force 20 is preferred to break intersheet coupling forces. For example, in FIGS. 5A through 5C, the force 20 diminishes from point 45 toward point 48 yet separation of the bunched sheets 31, 32 and 33 can occur. To put it otherwise, pad 10 can stop sheets 32 and 33 at points 47 and 48 even though the force 20 is diminishing between those two points. The force distribution is like that of curve 42 in FIG. 4 and the thumb-forefinger experiment is helpful in appreciating why this is so. The thumb-forefinger experiment may also be used to explain the reliability of the instant method and apparatus. Even with very high pinching force 20 the sheets cannot curl or wrinkle because they are completely enveloped by the throat 4. The belt pulls multiple sheets into the throat, the underlying sheets keep the outer sheets from buckling and the clamping of the sheets in the throats creates a stiff column that resists bending.

Jaw 17 includes the vertical wall 49 that abuts sheets down further in the stack to limit their forward advance while the operation in FIGS. SA-C is taking place. The

tongue 18 includes the sloped surface 50 which supports sheets such as sheets 36 and 37 on their way to the throat 4. Specifically, the tongue keeps the lead edges of sheets 36 and 37 from tucking downward between the jaw and stack edge.

FIG. 6 illustrates another important aspect of the instant invention. In this drawing, the outermost sheet 31 is to the right of line 14 leaving the underlying sheet 32 in contact with the belt. However, before sheet 32 exits the throat the outermost sheet 31 is pulled by sheet 32 into the belt contact region around line 14. When the belt engages sheet 31, the outermost sheet leap frogs sheet 32 and exits the throat ahead of sheet 32. Therefore, the apparatus 1 clearly is able to queue or aline sheets in single file corresponding to the position or order the sheets occupy in a stack.

Another important feature of the present invention is that the sheets are not distorted any substantial amount during the feeding operation. The belt section between the entrance and exit pulleys is deliberately left unsupported to permit a desired normal force 21 to be generated by mechanically biasing the retard means and unsupported belt section against one another. The biasing is easily accomplished when the belt is elastic. However, the curve to a retard means, such as the curve to surface 1 1, is slight when compared to the length of the belt section between the entrance and exit pulleys. In other words, surface 11 is arched but comparatively linear over the region of contact between belt and retard means, i.e. in the throat 4. This general linearity of the throat prevents severe distortion to the sheets.

FIG. 7 illustrates a case where the radius of curvature of the surface of the retard means is sufficiently small to yield a significant non-linearity to the belt section between pulleys 8 and 9. The embodiment of FIG. 7 is still functional but is less desired because the sheets are bent through a relatively large angle in the throat. The bending is due to a large wrap distance 22 in combination with a short radius 24.

The best results are obtained when the linearity of the belt section between the entrance and exit pulleys is not substantially altered after the belt is biased against the retard means. This condition holds as long as the radius of the retard means, e.g. surface 11 in FIG. I, is greater than half the length of the linear belt section. The linear section of the belt is generally equal to the distance between the axes of the entrance and exit pulleys. I

The linearity feature of the instant invention, i.e. of the throat, means that a sheet is able to exit a stack in about the same plane as it occupied in the stack. FIGS. 1, 8, 11, 12, 13, 15 and 16 illustrate feeding methods and apparatus wherein the stack is raised to the level of the linear section of the belt 2. For these cases, the system being served by the feeder always receives a sheet from the same location. The feeding method and apparatus of FIG. 14 shows a situation where the belt 2 is moved to follow the shrinking height of the stack. In this case, the system being served must be able to cope with sheets being delivered to it from a plurality of locations.

The belt- 2 in FIG. 1 also advances a separated and queued sheet but this operation can be assisted by other drive or feed means. In FIGS. 1 and 14, the exit pulley includes friction tires 52 and 53 (FIG. 18) which extend beyond the belt 2. The tires abut against an idle roller 54 spring biased against them. The combination of tire and idle roller comprises a pinch drive. Preferably, the feeding apparatus also includes an external or separate pinch drive such as rollers 56 and 57 in FIGS. 11, l2, l3, l and 16. These external pinch rollers are driven at a higher speed than belt 2 to pull the sheets from the grasp of apparatus 1. The exit pulley should include a one way slip clutch such as a needle clutch to permit any drive coupled to it to be overcome by the action of the external pinch rollers.

The sheets, e.g. sheet 31 in FIG. 5C, travel through the throat 4 at a velocity less than that of the belt. The difference in velocity is due primarily to the retard force exerted by that portion of pad not covered by the underlying sheets such as sheets 32-35. The underlying sheets do, of course, also contribute to the differential in velocity between sheet 31 and the belt.

The foregoing difference in velocity between the belt and outermost sheet is the reason belt 2 is subject to wear. However, the wear feature also means that the surface of an endless belt 2 is continuously cleaned by the sheets it is feeding. Likewise, the pad 10 is continuously worn and cleaned by the sheets fed past it. The wear rate of the pad is much greater than that of the belt because the pad is constantly abraded by a plurality of sheets while the belt handles only the outermost sheet.

For the present method and apparatus to yield the best results the normal force 20 between the belt and retard means should be held constant for long feed runs. Force 20 is subject to change as wear reduces the belts thickness and due to aging of the rubber (synthetic or natural) which causes a change in resiliency and elasticity. For these and other reasons, it is preferred that the belt include an elastic material, e.g. natural or synthetic rubber, molded to a woven belt substrate made from a comparatively non-elastic material, e.g. dacron or rayon.

The belt, according to the recommended structure, is shown in cross-section in FIG. 19. The layer of natural rubber 60 is about 0.100 inch thickness comprises the belt portion contacting the retard means. The belt is about 0.625 inch wide. Layer 60 is molded to the rayon cord belt 61 which is about 0.015 inch thick. Also molded to the rayon cord material 61 is the tracking member 62 made of an elastic material such as neoprene. The tracking member includes a truncated triangular rib 63 which rides in mating grooves in the entrance and exit pulleys 8 and 9.

The fiber reinforced belt in FIG. 19 may also have a tire tread pattern of grooves in the layer 60. See FIG. 17. The tire pattern includes two or more zig-zag grooves 64 formed in the surface of the belt that abuts the retard means. The zig-zag grooves extend generally along the length of the belt to improve traction and to allow quick escape for contaminants from the surface of the belt. Also, the grooves eliminate an airbearing effect at higher belt speeds which can substantially lower traction between the belt and a sheet.

The fiber reinforced belt is better suited for grooving than an all elastic belt. The grooves in an all elastic belt tend to open when the belt is stretched over the supporting pulleys including entrance and exit pulleys 8 and 9. The grooves 64 in a reinforced belt or even in a non-reinforced belt, however, should be very narrow to prevent the lead edge ofa weak piece of paper from entering the grooves.

Another reason why an elastic belt, whether reinforced or not, is preferred over a non-elastic belt is that the elastic belt is more permissible to shingling of sheets in the mouth 23 to the queuing throat. The shingling of sheets, e.g. see thecondition of sheets 36 and 37 in FIG. 5B, in the mouth is desirable because the underlying sheets partially protect the retard means, e.g. pad 10, from frictional wear against the belt. The mouth shape may be changed to help shingling for different type sheet materials as indicated earlier. The elastic belt in all these mouth shapes prevents undesirably high pressure points from building up due to the presence of the shingled sheets. The pressure build up is prevented because the elastic belt expands. The expansion and contraction feature of the elastic belt (reinforced or not) enables it to be mounted about as few as two pulleys. A non-elastic belt is difficult to keep under tension with only two pulleys.

FIG. 8 is a feeding apparatus using a non-elastic (comparatively) belt 2. The third pulley 67 is one of many schemes whereby tension is maintained in the lin ear section 68. The third pulley is supported at the free end of a pivoted arm 69. The arm is mechanically biased counterclockwise by the coil spring 70 thereby constantly maintaining tension in the belt 2 yet leaving the belt sufficiently flexible to mate with the curved surface 11 on the retard pad 10.

Skew control of sheets is not a significant problem in the instant sheet handling systems. One reason for this is that only a single combination of separation belt and mating retard means is used. When multiple separation belts are used, mismatches in forces give rise to the skewing sheet problems. In fact, the present concept of limiting sheet contact to very small areas almost eliminates all sheet skewing. However, the small area contact permits a sheet to be turned or pivoted about a point located in the queuing throat. This is very beneficial to sheet handling systems employing a sheet registration device up stream from apparatus 1.

FIG. 11 disclosed the apparatus 1 of FIG. 1 used with a steering wheel 71 which controls the direction of the sheets in the plane in which they are being handled. The steering wheel is a relatively narrow width roller having a friction surface and which is biased against the stack at a location toward its opposite edge from apparatus l. The steering wheel is intended to control the direction of the outermost sheet until it is gripped by the pinch rollers 56 and 57. The steering wheel is, of course, purely optional.

Turning now to FIG. 9, the retard means illustrated throughout includes a pad 10. In FIG. 16, the pad has a movable web placed over it to compensate for wear. The pad 10, support plate 72 and tongue-jaw member 17 18 is shown in exploded view in FIG. 9. The pad surface 11 is also grooved to minimize Wear, for cleaning and to minimize the airbearing effect." The pad is made of a resilient material such as rubber (natural or synthetic). The pad is appropriately secured to the support plate, e.g. by a glue, and has a notch 73 for mating with the jaw-tongue member 17-18. The surface 11 flows continuously into the slope of the tongue 18. The surface 1 1 is most commonly a cylindrical surface but may be a more complex curved surface and may include planar sections. It is relatively long compared to its thickness to permit a long throat length, i.e. wrap distance 22, while keeping the throat rather linear. In other words, if the retard means is a full cylindrical roller, it is difficult to control the length of the throat without greatly altering its linearity or flatness. The large deviation from the near linear shape means excessive distortion to the sheets. Also a roller of sufficiently large diameter cannot easily be positioned against the edge of the stack like pad 10 without creating a very large mouth and without making the distance between the throat and line 14 (the contact region between belt and stack) very large.

The width of the retard means is preferably less than the width of the belt. See FIG. 10. The arrangement of FIG. 10 is preferred because the edges of the retard means, pad 10 in this case, are opposed by the feed belt. If the belt is narrower than the retard means, the sheets are subjected to compound deflections. Matching the width of the belt and retard means creates the practical problem of keeping the two aligned. The belt overlap condition of FIG. 10 does not cause excessive wear, doesnt subject the sheets to undesirable deflections and permits some misalignment between the belt and retard means.

The retard surface 11 is preferably a soft rubber of about 40 durometerrating. This resiliency or softness permits the lead edge of the sheets to dig into the retard means. See FIG. 5C for example. The retard means should'not be too soft, however, or wear will be excessive. For this reason, the retard means is grooved, e.g. see grooves in FIG. 9, to give it mechanical softness, resiliency or flexibility yet the durometer of the material is high to minimize wear.

Another reason that the radius 24 of the retard is kept relatively large is to minimize a capstan action. For example, the small radius (less than half the distance between the pulleys 8 and 9) of the pad 10 in FIG. 7 is at or near a radius condition giving rise to large wrap angle 77 of the belt about the pad. This large wrap angle aids the digging in of the lead edge of the sheets into the pad. However, the large angle approaches the case where the effect is too great and a capstan action can cause distortion to a sheet.

FIGS. 12, 13, 14, 15 and 16 represent different environments for the instant sheet feeding system. FIG. 12 illustrates a device where the separation belt 2 is of a finite length mounted on an endless slip belt 79 made of steel for example. This apparatus permits intermittent sheet feeding because no sheets are handled when the finite belt is not in contact with the stack. By properly selecting the length of the slip belt 79, a predetermined spacing can be established between the sheets separated, queued and advanced.

The apparatus of FIG. 13 illustrates a pivot mounting 80 for the tray 13. The pivot point is near the end of the tray opposite apparatus 1. The coil spring 81 mechanically biases the tray toward the entrance pulley 8. The apparatus 1 itself is oriented to feed sheets in a plane generally 30 degrees from horizontal.

FIG. 14 depicts apparatus 1 suspended to move against the stack as the stack is consumed by the feeding operation. Apparatus 1 is coupled to the end of support beam 83 which is pivotally supported at pin 84. The weight of apparatus 1 biases the feeder against the stack during the feeding operation. The coil spring 85 is present to lessen the force on the stack to something less than the weight of apparatus 1. The tray 13 is stationary in this case.

FIG. 15 illustrates an environment wherein sheets are fed vertically from a stack standing on edge. The tray 13 includes a roller 88 positioned on an inclined plane 89 enabling gravity to bias the stack 5 against the idle wheels 90 and separation belt 2. The dashed line 91 indicates a position that facilitates loading the stack into the tray.

FIG. 16 illustrates several variations to apparatus 1. The most apparent is the use of a third pulley 94. Also, the entrance pulley 8 and third pulley 94 are substantially smaller than the exit pulley 9. The tray 13 is pivoted about a post 95 located to the left of its center of gravity. The post is a fulcrum that gives mechanical advance for biasing the tray and a stack upward against the belt 2. In addition, the jaw member 96 in this view is curved to accommodate the arc followed by the tray as it pivots clockwise under its own weight. Another significant difference is the web 97 wound over surface 11 of pad 10 and the drive pulley 98. The web provides the wear surface for the retard means and is advanced at a speed differing from the speed of the belt 2 by pulley 98. For example, web 97 may be rotated clockwise at a rate of one revolution per hour. It should be noted,

however, that web 97 may be incrementally advanced rather than continuously. It is preferred, but not necessary, to rotate web 97 in the opposite direction of belt 2. The embodiment of FIG. 16 also illustrates by dashed lines 99 a severe angle between the stack and throat 4 that is possible in the present invention.

Returning now to FIG. 2, the entrance and exit pulleys 8 and 9 are shaped differently on their peripheries contacting the belt. The exit, and usually the drive pulley 9, is substantially cylindrical in that it keeps the belt surface contacting the sheets cylindrical as it passes around the pulley. On the other hand, the entrance pulley is beveled or ballooned on its surface, see surface 100 in FIG. 2, such that the belt surface contacting the sheets is bowed as it passes around the entrance pulley. This feature helps belt tracking and, in the case of elastic belts, enables the belt to more efficiently grab the sheets to pull them from the stack.

Other modifications and variations to the presently disclosed embodiments are possible. All such changes which stay within the spirit of this invention are intended to be encompassed herein.

What is claimed is:

1. In sheet feeding and separating apparatus for feeding and separating individual sheets from a stack of sheets at an edge of the stack the improvement comprising:

an endless sheet feeding and separating belt mounted for sheet feeding engagement with the edge of the stack of sheets.

said feed belt being rotatably mounted between spaced supports to provide a deformable unsupported section therebetween,

a retard member having a supported finitely curved frictional retard surface, said retard surface deformably engaging said fe'ed belt in said unsupported section of said feed belt to form therewith a correspondingly curved sheet queuing throat in which said retard surface and said belt are continuously mechanically biased against one another,

said sheet queuing throat being positioned directly adjacent the edge of the stack and said feed belt operatively extending over only the edge of the stack, cooperatively preventing buckling of sheets fed from the stack by said feed belt into said sheet queuing throat.

2. The apparatus of claim 43 wherein said curved retard surface of said retard member has a large radius of curvature which is greater than the distance between a different material, curving away from said feed belt I at said stack edge and smoothly transitioning into said curved retard surface of said retard member, to assist in guiding sheets from the stack directly into said queuing throat.

5. The apparatus of claim 43 wherein said feed belt is deformable and made of an elastic material but is reinforced by comparatively non-elastic fibrous material.

6. The apparatus of claim 43 wherein said curved retard surface of said retard member has a radius of curvature greater than half the length of said unsupported section of said feed belt.

7. The apparatus of claim 43 wherein said retard member is a curved ribbed pad of resilient frictional material.

8. The apparatus of claim 43 wherein said retard member comprises an endless flexible retard belt of resilient frictional material and an underlying nonrotating curved supporting guide directly adjacent the stack edge and defining said queuing throat, wherein said retard belt is conformably slidably mounted over said guide.

9. The apparatus of claim 43 wherein said feed belt is pivotally mounted to move with the stack level and said retard member is movably mounted to provide movement of said retard member together with said feed belt when said feed belt moves with the stack without disturbing said engagement of said retard member with said feed belt.

10. The apparatus of claim 51 wherein said feed belt said spaced supports and said retard member are an integral unit pivotally mounted to rotate as a unit relative to the stack.

11. The apparatus of claim 43 wherein said curved retard surface of said retard member has a large radius of curvature which is greater than the distance between said retard surface and the edge of the stack, and

said curved retard surface of said retard member has a radius of curvature greater than half the length of said unsupported section of said feed belt.

l l =l Patent No. 3 7 3 Datedggtgber 3 1&13

Inventor(s) Klaus K. Stange It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Claim 8, line Claim 7, line 1, change "43" to-l--.

1, change "43" to-l-.

Claim 9, line change "43" to-l-.

Claim 10, line 1, change "51" to--9--.

Claim 11, line 1, change "4-3" tol-.

Signed and sealed this 16th day of April 19714,.

(SEAL) Attest:

EDWARD M.FIETCHER,TE1. C. MARSHALL DANN V Attesting Officer Commissioner of Patents USCOMM-DC 60S76-P69 i U. S. GOVERNMENT PRINTING OFFICE l9. 0-866-38L 

1. In sheet feeding and separating apparatus for feeding and separating individual sheets from a stack of sheets at an edge of the stack the improvement comprising: an endless sheet feeding and separating belt mounted for sheet feeding engagement with the edge of the stack of sheets, said feed belt being rotatably mounted between spaced supports to provide a deformable unsupported section therebetween, a retard member having a supported finitely curved frictional retard surface, said retard surface deformably engaging said feed belt in said unsupported section of said feed belt to form therewith a correspondingly curved sheet queuing throat in which said retard surface and said belt are continuously mechanically biased against one another, said sheet queuing throat being positioned directly adjacent the edge of the stack and said feed belt operatively extending over only the edge of the stack, cooperatively preventing buckling of sheets fed from the stack by said feed belt into said sheet queuing throat.
 2. The apparatus of claim 1 wherein said curved retard surface of said retard member has a large radius of curvature which is greater than the distance between said retard surface and the edge of the stack.
 3. The apparatus of claim 1 wherein a side of said retard member diverges from said feed belt directly adjacent said queuing throat to provide a stack edge stop jaw for the stack.
 4. The apparatus of claim 1 wherein said retard member includes an integral curved tongue member of a different material, curving away from said feed belt at said stack edge and smoothly transitioning into said curved retard surface of said retard member, to assist in guiding sheets from the stack directly into said queuing throat.
 5. The apparatus of claim 1 wherein said feed belt is deformable and made of an elastic material but is reinforced by comparatively non-elastic fibrous material.
 6. The apparatus of claim 1 wherein said curved retard surface of said retard member has a radius of curvature greater than half the length of said unsupported section of said feed belt.
 7. The apparatus of claim 1 wherein said retard member is a curved ribbed pad of resilient frictional material.
 8. The apparatus of claim 1 wherein said retard member comprises an endless flexible retard belt of Resilient frictional material and an underlying non-rotating curved supporting guide directly adjacent the stack edge and defining said queuing throat, wherein said retard belt is conformably slidably mounted over said guide.
 9. The apparatus of claim 1 wherein said feed belt is pivotally mounted to move with the stack level and said retard member is movably mounted to provide movement of said retard member together with said feed belt when said feed belt moves with the stack without disturbing said engagement of said retard member with said feed belt.
 10. The apparatus of claim 9 wherein said feed belt said spaced supports and said retard member are an integral unit pivotally mounted to rotate as a unit relative to the stack.
 11. The apparatus of claim 1 wherein said curved retard surface of said retard member has a large radius of curvature which is greater than the distance between said retard surface and the edge of the stack, and said curved retard surface of said retard member has a radius of curvature greater than half the length of said unsupported section of said feed belt. 